When running as Xen PV guest, masking MSI-X is a responsibility of the hypervisor. Guest has no write access to relevant BAR at all - when it tries to, it results in a crash like this:
BUG: unable to handle page fault for address: ffffc9004069100c #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 18f1c067 P4D 18f1c067 PUD 4dbd067 PMD 4fba067 PTE 80100000febd4075 Oops: 0003 [#1] SMP NOPTI CPU: 0 PID: 234 Comm: kworker/0:2 Tainted: G W 5.14.0-rc7-1.fc32.qubes.x86_64 #15 Workqueue: events work_for_cpu_fn RIP: e030:__pci_enable_msix_range.part.0+0x26b/0x5f0 Code: 2f 96 ff 48 89 44 24 28 48 89 c7 48 85 c0 0f 84 f6 01 00 00 45 0f b7 f6 48 8d 40 0c ba 01 00 00 00 49 c1 e6 04 4a 8d 4c 37 1c <89> 10 48 83 c0 10 48 39 c1 75 f5 41 0f b6 44 24 6a 84 c0 0f 84 48 RSP: e02b:ffffc9004018bd50 EFLAGS: 00010212 RAX: ffffc9004069100c RBX: ffff88800ed412f8 RCX: ffffc9004069105c RDX: 0000000000000001 RSI: 00000000000febd4 RDI: ffffc90040691000 RBP: 0000000000000003 R08: 0000000000000000 R09: 00000000febd404f R10: 0000000000007ff0 R11: ffff88800ee8ae40 R12: ffff88800ed41000 R13: 0000000000000000 R14: 0000000000000040 R15: 00000000feba0000 FS: 0000000000000000(0000) GS:ffff888018400000(0000) knlGS:0000000000000000 CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8000007f5ea0 CR3: 0000000012f6a000 CR4: 0000000000000660 Call Trace: e1000e_set_interrupt_capability+0xbf/0xd0 [e1000e] e1000_probe+0x41f/0xdb0 [e1000e] local_pci_probe+0x42/0x80 (...)
There is pci_msi_ignore_mask variable for bypassing MSI(-X) masking on Xen PV, but msix_mask_all() missed checking it. Add the check there too.
Fixes: 7d5ec3d36123 ("PCI/MSI: Mask all unused MSI-X entries") Cc: stable@vger.kernel.org Signed-off-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com --- Cc: xen-devel@lists.xenproject.org
Changes in v2: - update commit message (MSI -> MSI-X) --- drivers/pci/msi.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index e5e75331b415..3a9f4f8ad8f9 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -776,6 +776,9 @@ static void msix_mask_all(void __iomem *base, int tsize) u32 ctrl = PCI_MSIX_ENTRY_CTRL_MASKBIT; int i;
+ if (pci_msi_ignore_mask) + return; + for (i = 0; i < tsize; i++, base += PCI_MSIX_ENTRY_SIZE) writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL); }
On Thu, Aug 26, 2021 at 07:03:42PM +0200, Marek Marczykowski-Górecki wrote:
When running as Xen PV guest, masking MSI-X is a responsibility of the hypervisor. Guest has no write access to relevant BAR at all - when it tries to, it results in a crash like this:
BUG: unable to handle page fault for address: ffffc9004069100c #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 18f1c067 P4D 18f1c067 PUD 4dbd067 PMD 4fba067 PTE 80100000febd4075 Oops: 0003 [#1] SMP NOPTI CPU: 0 PID: 234 Comm: kworker/0:2 Tainted: G W 5.14.0-rc7-1.fc32.qubes.x86_64 #15 Workqueue: events work_for_cpu_fn RIP: e030:__pci_enable_msix_range.part.0+0x26b/0x5f0 Code: 2f 96 ff 48 89 44 24 28 48 89 c7 48 85 c0 0f 84 f6 01 00 00 45 0f b7 f6 48 8d 40 0c ba 01 00 00 00 49 c1 e6 04 4a 8d 4c 37 1c <89> 10 48 83 c0 10 48 39 c1 75 f5 41 0f b6 44 24 6a 84 c0 0f 84 48 RSP: e02b:ffffc9004018bd50 EFLAGS: 00010212 RAX: ffffc9004069100c RBX: ffff88800ed412f8 RCX: ffffc9004069105c RDX: 0000000000000001 RSI: 00000000000febd4 RDI: ffffc90040691000 RBP: 0000000000000003 R08: 0000000000000000 R09: 00000000febd404f R10: 0000000000007ff0 R11: ffff88800ee8ae40 R12: ffff88800ed41000 R13: 0000000000000000 R14: 0000000000000040 R15: 00000000feba0000 FS: 0000000000000000(0000) GS:ffff888018400000(0000) knlGS:0000000000000000 CS: e030 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8000007f5ea0 CR3: 0000000012f6a000 CR4: 0000000000000660 Call Trace: e1000e_set_interrupt_capability+0xbf/0xd0 [e1000e] e1000_probe+0x41f/0xdb0 [e1000e] local_pci_probe+0x42/0x80 (...)There is pci_msi_ignore_mask variable for bypassing MSI(-X) masking on Xen PV, but msix_mask_all() missed checking it. Add the check there too.
Fixes: 7d5ec3d36123 ("PCI/MSI: Mask all unused MSI-X entries") Cc: stable@vger.kernel.org Signed-off-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com
Acked-by: Bjorn Helgaas bhelgaas@google.com
Cc: xen-devel@lists.xenproject.org
Changes in v2:
- update commit message (MSI -> MSI-X)
drivers/pci/msi.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index e5e75331b415..3a9f4f8ad8f9 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -776,6 +776,9 @@ static void msix_mask_all(void __iomem *base, int tsize) u32 ctrl = PCI_MSIX_ENTRY_CTRL_MASKBIT; int i;
- if (pci_msi_ignore_mask)
return;- for (i = 0; i < tsize; i++, base += PCI_MSIX_ENTRY_SIZE) writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL);
}
2.31.1
The following commit has been merged into the irq/urgent branch of tip:
Commit-ID: 1a519dc7a73c977547d8b5108d98c6e769c89f4b Gitweb: https://git.kernel.org/tip/1a519dc7a73c977547d8b5108d98c6e769c89f4b Author: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com AuthorDate: Thu, 26 Aug 2021 19:03:42 +02:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Fri, 27 Aug 2021 00:27:15 +02:00
PCI/MSI: Skip masking MSI-X on Xen PV
When running as Xen PV guest, masking MSI-X is a responsibility of the hypervisor. The guest has no write access to the relevant BAR at all - when it tries to, it results in a crash like this:
BUG: unable to handle page fault for address: ffffc9004069100c #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation RIP: e030:__pci_enable_msix_range.part.0+0x26b/0x5f0 e1000e_set_interrupt_capability+0xbf/0xd0 [e1000e] e1000_probe+0x41f/0xdb0 [e1000e] local_pci_probe+0x42/0x80 (...)
The recently introduced function msix_mask_all() does not check the global variable pci_msi_ignore_mask which is set by XEN PV to bypass the masking of MSI[-X] interrupts.
Add the check to make this function XEN PV compatible.
Fixes: 7d5ec3d36123 ("PCI/MSI: Mask all unused MSI-X entries") Signed-off-by: Marek Marczykowski-Górecki marmarek@invisiblethingslab.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Bjorn Helgaas bhelgaas@google.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210826170342.135172-1-marmarek@invisiblethingsla... --- drivers/pci/msi.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c index e5e7533..3a9f4f8 100644 --- a/drivers/pci/msi.c +++ b/drivers/pci/msi.c @@ -776,6 +776,9 @@ static void msix_mask_all(void __iomem *base, int tsize) u32 ctrl = PCI_MSIX_ENTRY_CTRL_MASKBIT; int i;
+ if (pci_msi_ignore_mask) + return; + for (i = 0; i < tsize; i++, base += PCI_MSIX_ENTRY_SIZE) writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL); }
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